Valuable knowledge relating to the characteristics of transmitted light may be learned by studying a beam of transmitted light. It would be helpful to those studying the physics of light if stable means to demonstrate the passage of a beam of light through a transparent medium were available. However, transmitted light, such as a light beam, cannot be seen as it passes through a vacuum or a clear homogeneous medium, such as a colorless gas or liquid, like air or water. A beam of light passing through empty space or a clear homogeneous liquid is only visible when it is scattered by, i.e. reflected off the surface of, an object in the space or liquid. The object which scatters the light beam may be large, such as a piece of furniture, or very tiny, such as a minute particle of matter.
A currently practiced method of rendering a beam of light visible in a chamber involves the creation of a suspension of fine particles in the chamber and passing the beam of light through the chamber. The beam of light becomes visible as it reflects off the surfaces of the particles. For example, a beam of light has been studied by transmitting it through a chamber in which a fog was created by the evaporation of liquefied carbon dioxide in the chamber. The rapid evaporation of the carbon dioxide causes moisture in the chamber to condense into tiny droplets of water which are capable of scattering a beam of light passing through the chamber, thereby making the light visible. Similarly, a beam of light has been made visible in a closed chamber by injecting a small amount of smoke into the chamber. The smoke renders the light beam visible as it passes through the chamber. Unfortunately, the fog and smoke used in these techniques are short-lived and the procedure has to be continuous or frequently repeated to maintain an atmosphere in the chamber in which the beam of light is visible.
Because of the educational and scientific benefits and advantages derived from the examination of a beam of light, there is a continuing search for improved apparatus and methods for displaying a lightbeam as it passes through a medium.